Low resistivity metal layers minimize power losses and overheating in integrated circuit designs. Resistivity is an intrinsic property of a material and a measurement of a material's resistance to the movement of charge through the material. The resistivity of a material affects the electrical operation of an integrated circuit.
The deposition of tungsten layers using chemical vapor deposition (CVD) techniques is an integral part of many semiconductor fabrication processes. Tungsten layers may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on the silicon substrate.
It is desirable to use low resistivity tungsten layers in conjunction with tungsten nitride layers, the low resistivity tungsten layer being deposited on top of the tungsten nitride layer. The tungsten nitride layer provides relatively low resistivity, good adhesion to dielectric layers, and is a good diffusion barrier. Problems regarding the use of low resistivity tungsten layers with tungsten nitride layers, however, have prevented these materials from being used together in semiconductor devices.